Network configuration overview

Learn concepts and terms to help you better understand how to configure your network in IBM® Cloud Pak System so it meets your requirements.

Basic concepts

VLAN
A virtual LAN (VLAN) is an isolated broadcast domain that is created within a switch. Each VLAN created within a switch is isolated from other VLANs. The network traffic can pass from one VLAN to another by adding a routing device. The routing functions must be provided at the data center core network.
VLAG
A Virtual Link Aggregation Group (VLAG) allows for multi-system link aggregation and facilitates active-active uplinks of access layer switches.
To ensure high availability for the system, IBM Cloud Pak System requires VLAG and link aggregation for the switches.
Layer 2 connections
The connections from all the IBM Cloud Pak System Top of Rack (ToR) switches to the data center core network and customer management network are all layer 2 connections. IBM Cloud Pak System supports the Link Aggregate Control Protocol (LACP) type of layer 2 aggregation.
The following characteristics describe layer 2 connections:
  • Layer 2 is considered switching and is done at the hardware layer.
  • Layer 2 is in the same broadcast domain or local network.
  • Layer 2 finds adjacent partners by MAC address.
Layer 3 connection
IBM Cloud Pak System does not participate in any layer 3 routing or firewall functions. These functions are done in the data center core network.
The following characteristics describe layer 3 connections:
  • Layer 3 is considered routing and is done at the software layer.
  • Layer 3 knows how to traverse multiple networks (hops).
  • Layer 3 finds adjacent partners by IP address.
Spanning tree
Note: You can no longer create links without Spanning Tree. The IBM Cloud Pak System user interface does not have the checkbox to select the Spanning Tree option. By default, it is enabled.

Aggregation methods

IBM Cloud Pak System supports the following aggregation methods for the connections on the customer data network:
LACP
The standard-based negotiation protocol, which is known as IEEE 802.1ax Link Aggregation Control Protocol (LACP), is a way to dynamically build an Etherchannel. LACP is implemented in the switch by way of Linux bonding. Linux bonding provides a method for aggregating multiple network interfaces (members) into a single logical bonded interface (bond). Link aggregation is useful for linear scaling of bandwidth, load balancing, and failover protection.
No aggregation
If aggregation is not possible, this method is available, but not suggested, to provide high availability with no aggregation. With this method, it is suggested to enable PVRST to avoid loops. When this method is used and PVRST is enabled, one of the links is deactivated by STP, while the other link is enabled. This method is also called Aggregation None.

Port types

Access
An access port provides access to a single VLAN only. Typically, the packets on an access port are raw Ethernet frames (untagged packets). An access port can accept packets that are tagged if the VLAN ID in the tagged frame matches the PVID of the access mode port. Otherwise, the packet is dropped.
Trunk
A trunk connection is used to pass traffic from multiple VLANs between two switches across an ISL (Inter-Switch Link). All trunks use the IEEE 802.1Q standard. This link can be a single wire or one of the aggregations methods in Aggregation methods.